Nathan Smith has launched 960.gs, a very promising framework and design toolset for layout using CSS. Besides a great foundation of code for implementing a flexible grid system, he’s created accompanying templates for sketching preliminary designs on paper and wireframing detailed designs in Visio, OmniGraffle, Fireworks, and/or Photoshop. As with any Nathan Smith endeavor, this kit is very well thought-out and executed. He’s considered many details and implemented them thoroughly.
If you’re looking to cut down development time while sketching, wireframing, or coding hi-fi prototypes in HTML, Nathan’s work in the 960.gs is sure to be a great starting point.